The invention relates to asphalt compositions and, more particularly, to a method for preparing an asphalt compositions which has good performance characteristics within a given temperature range.
Asphalt compositions are used in various applications, one predominant application of which is the paving industry. During normal use, pavement tends to show several distresses, including temperature induced permanent deformation or rutting, low temperature-induced thermal cracking, load associated fatigue cracking and chemical aging or hardening.
Growing traffic and higher axial loads of vehicles accelerate this road damage.
In an attempt to address these problems, polymers have been added to the asphalt. Unfortunately, compatibility of the polymer and effective incorporation of the polymer into the asphalt, as well as stability of the asphalt composition prior to use, remain issues with known methods.
In order to obtain dispersion of the typically solid polymer through the asphalt, a high shear mixing is required. Even with such high shear mixing, the dispersion so obtained is unstable.
Vulcanizing agents such as sulfur have also been used in asphalt compositions. Although various methods of incorporating sulfur into the asphalt composition have been attempted, problems experienced include the generation of H2S gases at temperatures above certain levels, the need for high shear mixing equipment, and persistent phase separation.
Attempts to incorporate sulfur into pavement during pavement construction result in sulfur incorporated as an aggregate, and not as a component of the asphalt itself. Thus, problems remain in connection with suitable incorporation of sulfur into the asphalt composition as well.
Based upon the foregoing, it is clear that the need remains for an improved method for preparation of an asphalt composition whereby polymers and/or sulfur can effectively be incorporated into the asphalt composition.
It is therefore the primary object of the present invention to provide such a method.
It is a further object of the present invention to provide such a method wherein the resulting asphalt composition is stable under asphalt storing conditions.
It is still another object of the present invention to provide such a composition wherein effective dispersion of the ingredients added to the asphalt results in a final product having desirable characteristics in connection with resistance to rutting, low temperature cracking, fatigue cracking and chemical aging or hardening.
Other objects and advantages of the present invention will appear hereinbelow.